Studies On The Applications Of (E)-α-Bromovinylselenides And (Z)-α-Silylvinyl Grignard Reagents In Stereoselective Synthesis Of Substituted Alkenes

This dissertation consists of two parts:Part one:We investigated that the reaction of alkynyl Grignard reagents with arylselanyl bromides afforded alkynyl selenides in high yield,which underwent addition with hydrogen bromide to give stereose-lectively (E) - a - bromovinylselenides. We developed a novel approach to the stereoselective synthesis of (Z) -1,3- enynylselenides by the cross - coupling reaction of (E) - a - bromovinylselenides and alkynyl Grignard reagents in the presence of palladium catalyst. We studied that (Z) - a - selanyl alkenyl Grignard reagents were reacted with alkyl or aryl iodides in the presence of Cul or Pd(PPh3)4 catalysts to give stereos-electively (Z) - 1,2 - disubstituted vinylselenides,which can undergo NiCl2 (PPh3 )2 - catalyzed cross - coupling reaction with Grignard reagents,providing a convenient approach to the stereoselective synthesis of trisubstituted alkenes.Part two:(Z) - a - silylvinyl Grignard reagents were prepared by the hydromagnesiation of alkynylsilanes. The reaction of (Z) - a -silylvinyl Grignard reagents with aldehydes and ketones were investigated and the corresponding (Z) - 2 - silylallylic alcohols were obtained in high yields. (Z) - 2 - silylallylic alcohols can undergo a desilylation reaction in the presence of KF in DMSO to afford a practical procedure for stereoselective synthesis of a variety of (E) -allylic alcohols.